1. Field of the Invention
The present invention relates to an explosive primer, and to a carrier for supporting the primer explosive charge therein in operative relationship to initiating means for the charge. More particularly, the invention relates to a carrier adapted, in one embodiment, to support a primer explosive charge, a percussion-actuated detonator operatively connected thereto, and an explosive coupler adapted to transmit an initiating impulse to said detonator from a low-energy detonating cord.
2. Description of the Prior Art
High-energy primers (sometimes referred to as "boosters") are used to initiate relatively insensitive explosives and blasting agents such as ANFO (ammonium nitrate--fuel oil) products and certain water gels. The primers, in turn, may be initiated by an instantaneous or delay electric detonator, a 3.8-13 g/m detonating cord downline, or a non-electric delay detonator actuated by a low-energy detonating cord (LEDC) downline. In the deck-loading technique of delay blasting with a cap-insensitive explosive loaded into the borehole in decks separated from one another by a layer of inert stemming material, each deck may require a delay primer (e.g., a primer operatively connected to a delay detonator), in which a delay detonator is operatively connected to a downline cord. Systems in which the delay primers in all of the decks are connected by a single downline are preferred because the downline system is less complex and the borehole loading operation and hookup easier.
U.S. Pat. No. 4,295,424, issued to D. H. Smith et al., and Atlas Data Sheet 701: Deckmaster/Primemaster, Atlas Powder Company, Dallas, Tex., describe an open-ended container for a cast primer having a tubular conduit disposed longitudinally on its exterior for threading a 4-6 g/m downline detonating cord, multiple primer units being threadable on a single downline. The container has a transverse partition separating the cast primer charge in a bottom section from an upper section which houses an elongated L-shaped insert consisting of a flexible curved tube with a sensor on one end and a delay detonator on the other. The partition has an aperture to allow the detonator portion of the insert to be positioned in the primer charge on the side opposite the tubular conduit.
A delay booster container shown in U.S. Pat. No. Re. 30,621 and Austin Technical Data Bulletin ADP 1183, Austin Powder Company, Cleveland, Ohio, entitled Austin Delay Boosters is a cup having an axial aperture in its closed bottom end and an external downline channel. An elongated delay element, in the form of a delay detonator having the end of a pigtail cord crimped into its shell is used. The detonator portion of the delay element is inserted into a delay channel formed by a center bore in the cast primer charge, through the aperture in the bottom of the cup. The external downline channel receives the pigtail, which side-abuts a downline threaded through multiple boosters.